I checked covers33 and a few music sites I usually buy from, Ebay and Amazon and what I am wanting is 400 gauge polythene sleeves. I have 250 gauge ones just now but they are a bit too flimsy. Whenever I take a record off the shelf it can sometimes pull another record out too or if I'm putting it back it can end up rolling back so then you kind of need to hold the sleeve and push the record back and that is another thing I wanted to point out. The ones that I use have about an inch flap on the end of them. The way I store my records is so that the spine faces me but the spin is part of the opening, it's clearer for me to read and many people store them that way. It also means I can lift the record out a lot of times without even needing to lift the polythene sleeve out so ideally the shorter the better.
You can never trust independant sellers on Amazon but I seen this one.
http://www.amazon.co.uk/Vinyl-Record-Po ... hene+vinyl
And it's like some of the ones I see on pictures here. The way the flap at the end is short is how I'd like it but I can't really tell if the way they took that photo, they placed the record in the centre just a bit too much, I don't think the sleeves would have that big a gap all the way around. I've bought stuff second hand that came in the kind of sleeves I am looking for but there is no way to trace where it came from. Do you know what I mean? A polythene sleeve that fits a 12" record perfectly and doesn't leave a huge flap at the end. I wont get rid of the ones I have on my albums just now, I'll just use them for the rest of my 12" singles.